1. Field of the Invention
This invention relates to a sensing element for a vehicle load measuring device, and more particularly to a pin-shaped sensing element which is set in a pin or shaft to which a vehicle load is applied, to detect the vehicle load by using a shearing force applied to the pin or shaft. The invention relates further to methods of fixing a sensing element, and more particularly to a method of fixing a sensing element in which a hole is formed in a cylindrical pin or shaft to which a shearing force is applied by a vehicle load, and a strain detecting sensing element is fixedly fitted in the hole thus formed. The invention relates further to sensing elements and methods of fixing them, and more particularly to a strain detecting sensing element which is fitted in a hole formed in a cylindrical pin or shaft to which a shearing force is applied by a vehicle load, and a method of fixing the sensing element.
2. Related Art
Heretofore, a vehicle load measurement is given mainly to large vehicles such as trucks. This is to eliminate the difficulty that if a truck is over-loaded, then it is adversely affected in operating characteristic. Not only may a traffic accident may occur, but also the truck itself and the road itself be damaged.
In general, the vehicle load measurement is performed using a load measuring device set on the road as follows: That is, with a wheel of the vehicle set on a loading plate having a load converter, the wheel load or the axle load of the wheel is measured. The loads thus obtained are summed up to obtain a vehicle load. The total of the weights of persons on the truck and the weight of the truck are subtracted from the vehicle load thus obtained, to obtain the weight of the load on the truck.
The vehicle load measuring device is disadvantageous in the following points: The device is bulky, and is high in installation cost, and therefore not only the place where the device is to be installed but also the number of vehicle load measuring devices which can be installed is limited. Hence, the number of vehicles whose loads can be measured with the device is only a fraction of the total number of vehicles. That is, the conventional vehicle load measuring device is insufficient to prevent all the vehicles from over-loading.
In order to eliminate this difficulty, a so-called "self load meter" has been proposed in the art, which is designed as follows: A sensing element such as a strain gauge type sensor is welded onto the axle casing of a vehicle. The sensing element operates to detect the bending strain which, when a load on the load-carrying platform is applied to the axle, occurs with the axle. Thus, with the meter, each vehicle is able to measure its load by itself.
However, the self load meter of this type suffers from the following difficulty: When the axle is inclined for instance because the place such as a road where the vehicle is positioned is poor, then even if the load on the vehicle is maintained, the vector of the load applied to the axle changes, and accordingly the amount of strain of the sensing element changes, so that the resultant detection value is not correct.